feat(docker+sensing-server): refresh Docker publish + opt-in bearer-token API auth

Closes #520, #514, #443.

## #520 / #514 — stale Docker image, missing UI assets

`ruvnet/wifi-densepose:latest` was published before `ui/observatory*` and
`ui/pose-fusion*` were added; users see /app/ui missing those files and the
v0.6+ packet format doesn't reach the server. Two fixes:

1. `docker/Dockerfile.rust` now `RUN`s a build-time guard after `COPY ui/`
   that fails the build if `index.html` / `observatory.html` / `pose-fusion.html`
   / `viz.html` (or the `observatory/` / `pose-fusion/` / `components/` /
   `services/` directories) are missing, plus an exec-bit check on
   `/app/sensing-server`. A stale image can never be silently produced again.

2. New `.github/workflows/sensing-server-docker.yml` rebuilds + pushes on
   every change to the Dockerfile, the server crate, the signal/vitals/
   wifiscan crates, the workspace manifests, the `ui/` tree, or itself —
   plus `v*` tags and manual dispatch. Pushes to both `docker.io/ruvnet/
   wifi-densepose` AND `ghcr.io/ruvnet/wifi-densepose` with `latest` +
   `vX.Y.Z` + `sha-<short>` tags, then post-push smoke-tests the artifact:
   /health, /api/v1/info, the observatory + pose-fusion HTML, AND the
   bearer-auth path (no token → 401, wrong → 401, correct → 200). Uses the
   `DOCKERHUB_USERNAME`/`DOCKERHUB_TOKEN` repo secrets; ghcr.io rides on
   the workflow's GITHUB_TOKEN.

## #443 — sensing-server REST API auth model

QE security audit raised that 40+ /api/v1/* routes have no auth layer with
a default `0.0.0.0` bind. New `wifi_densepose_sensing_server::bearer_auth`
module + middleware:

  - Env-var-gated: `RUVIEW_API_TOKEN` unset/empty ⇒ middleware is a no-op
    (current LAN-mode behaviour preserved — **no default change**); set ⇒
    every `/api/v1/*` request must carry `Authorization: Bearer <token>`
    or the server returns 401.
  - Constant-time byte compare via local `ct_eq` (no new dep).
  - `/health*`, `/ws/sensing`, and `/ui/*` are intentionally never gated
    (orchestrator probes + local browsers).
  - Startup logs which mode is active and warns when auth is ON with a
    `0.0.0.0` bind.
  - 8 unit tests on the middleware via `tower::ServiceExt::oneshot`
    (sensing-server lib tests 191 → 199, 0 failures).

Verified locally: `cargo build --workspace --no-default-features` ✓,
`cargo test -p wifi-densepose-sensing-server --no-default-features` ✓.

Co-Authored-By: claude-flow <ruv@ruv.net>

.github/workflows/sensing-server-docker.yml

@@ -0,0 +1,164 @@
+name: wifi-densepose sensing-server → Docker Hub + ghcr.io
+
+# Build + publish the `wifi-densepose` sensing-server image to both Docker Hub
+# (`ruvnet/wifi-densepose`) and ghcr.io (`ghcr.io/ruvnet/wifi-densepose`) on:
+#   - push to main affecting the Dockerfile, the server crate, the UI assets,
+#     or this workflow itself,
+#   - tag push matching v* (release builds),
+#   - manual workflow_dispatch.
+#
+# Closes #520 and #514: the stale `:latest` is rebuilt and pushed automatically
+# whenever the surface that produces it changes, and the Dockerfile fails the
+# build if the observatory/pose-fusion UI assets ever go missing again.
+#
+# Secrets:
+#   DOCKERHUB_USERNAME — `ruvnet` (Docker Hub login name)
+#   DOCKERHUB_TOKEN    — Docker Hub access token with read/write/delete scope
+# (ghcr.io uses the workflow's GITHUB_TOKEN — no secret needed.)
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'docker/Dockerfile.rust'
+      - 'docker/docker-entrypoint.sh'
+      - 'v2/crates/wifi-densepose-sensing-server/**'
+      - 'v2/crates/wifi-densepose-signal/**'
+      - 'v2/crates/wifi-densepose-vitals/**'
+      - 'v2/crates/wifi-densepose-wifiscan/**'
+      - 'v2/Cargo.toml'
+      - 'v2/Cargo.lock'
+      - 'ui/**'
+      - '.github/workflows/sensing-server-docker.yml'
+    tags: ['v*']
+  workflow_dispatch: {}
+
+permissions:
+  contents: read
+  packages: write
+
+concurrency:
+  group: sensing-server-docker-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-publish:
+    name: build · push · smoke-test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          registry: docker.io
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Log in to ghcr.io
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Compute tags
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            docker.io/ruvnet/wifi-densepose
+            ghcr.io/ruvnet/wifi-densepose
+          tags: |
+            type=ref,event=branch
+            type=ref,event=tag
+            type=sha,format=short
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - name: Build + push
+        id: build
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: docker/Dockerfile.rust
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          platforms: linux/amd64
+
+      # ---------------------------------------------------------------------
+      # Smoke-test the freshly-pushed image:
+      #   1. UI assets that closed #520 are inside `/app/ui` (the Dockerfile's
+      #      RUN guard catches missing ones at build time, this re-checks the
+      #      pushed artifact post-hoc as belt-and-braces).
+      #   2. /health is up.
+      #   3. /api/v1/info returns 200 with no auth (LAN-mode default).
+      #   4. With RUVIEW_API_TOKEN set, /api/v1/info returns 401 without a
+      #      Bearer header, 200 with the correct one (the #443 auth middleware).
+      # ---------------------------------------------------------------------
+      - name: Smoke-test image assets + LAN-mode HTTP
+        run: |
+          set -euo pipefail
+          IMAGE="ghcr.io/ruvnet/wifi-densepose:sha-${GITHUB_SHA::7}"
+          docker pull "$IMAGE"
+          docker run --rm "$IMAGE" sh -c \
+            'ls /app/ui/observatory.html /app/ui/pose-fusion.html /app/ui/index.html /app/ui/viz.html >/dev/null'
+          docker run --rm "$IMAGE" sh -c 'ls -d /app/ui/observatory /app/ui/pose-fusion >/dev/null'
+
+          docker run -d --name sm -p 3000:3000 -e CSI_SOURCE=simulated "$IMAGE"
+          # Wait up to 30 s for /health.
+          for _ in $(seq 1 30); do
+            if curl -fsS http://127.0.0.1:3000/health >/dev/null 2>&1; then break; fi
+            sleep 1
+          done
+          curl -fsS http://127.0.0.1:3000/health
+          curl -fsS http://127.0.0.1:3000/api/v1/info >/dev/null
+          curl -fsS http://127.0.0.1:3000/ui/observatory.html >/dev/null
+          curl -fsS http://127.0.0.1:3000/ui/pose-fusion.html >/dev/null
+          docker stop sm
+
+      - name: Smoke-test the bearer-token auth path
+        run: |
+          set -euo pipefail
+          IMAGE="ghcr.io/ruvnet/wifi-densepose:sha-${GITHUB_SHA::7}"
+          docker run -d --name auth \
+            -p 3000:3000 \
+            -e CSI_SOURCE=simulated \
+            -e RUVIEW_API_TOKEN=smoke-test-token-do-not-use \
+            "$IMAGE"
+          for _ in $(seq 1 30); do
+            if curl -fsS http://127.0.0.1:3000/health >/dev/null 2>&1; then break; fi
+            sleep 1
+          done
+          # /health stays unauthenticated.
+          curl -fsS http://127.0.0.1:3000/health >/dev/null
+          # /api/v1/info without a bearer → 401.
+          code=$(curl -s -o /dev/null -w '%{http_code}' http://127.0.0.1:3000/api/v1/info)
+          test "$code" = "401" || { echo "expected 401, got $code"; exit 1; }
+          # Wrong bearer → 401.
+          code=$(curl -s -o /dev/null -w '%{http_code}' -H 'Authorization: Bearer wrong' http://127.0.0.1:3000/api/v1/info)
+          test "$code" = "401" || { echo "expected 401 (wrong token), got $code"; exit 1; }
+          # Correct bearer → 200.
+          curl -fsS -H 'Authorization: Bearer smoke-test-token-do-not-use' http://127.0.0.1:3000/api/v1/info >/dev/null
+          docker stop auth
+
+      - name: Summary
+        if: always()
+        run: |
+          {
+            echo "## sensing-server image published"
+            echo
+            echo "Tags:"
+            echo '```'
+            echo "${{ steps.meta.outputs.tags }}"
+            echo '```'
+            echo
+            echo "Closes #520 (missing observatory/pose-fusion UI assets) and #514 (stale `:latest` for the v0.6+ packet format)."
+            echo "The Dockerfile fails the build if those UI assets ever disappear again, and this workflow rebuilds + pushes automatically on every change to the surface."
+          } >> "$GITHUB_STEP_SUMMARY"